The biggest nuclear blast in history came courtesy of Tsar Bomba. We could make something at least 100 times more powerful.
This got Edward Teller, the “Father of the Hydrogen Bomb,” excited. In 1954, he apparently proposed a 10,000-megaton nuclear weapon to U.S. government officials.
“A 10,000-megaton weapon, by my estimation, would be powerful enough to set all of New England on fire. Or most of California. Or all of the UK and Ireland. Or all of France. Or all of Germany. Or both North and South Korea,” Alex Wellerstein, a historian of science and nuclear weapons and a professor at the Stevens Institute of Technology, wrote.
Thankfully, Teller’s fascinations were notoriously frenetic, and this idea soon fell by the wayside.
The limit is size and weight for delivery. Then available material. There is no actual limit to the size as I understand it.
Salted nukes are a much, much darker subject in my opinion. Designed to “salt the earth” with radiation and it’s the entire planet earth here, not some dirt earth.
Theoretically, there is no limit as long as you have the fuel to sustain it. Most of the yield from thermonuclear weapons actually comes from fusion, and not fission. With fission devices (i.e. what dropped on Japan at the end of WWII), you’re limited by efficiency because the energy release and explosion removes the required density of the fissile material, so the chain reaction naturally stops. Fusion devices have no such limitation, so you’re only really limited by how much fuel you have and your capacity to deliver the weapon on a target.
The second part of that question, though, is what do you do with it? While you can certainly scale up the yield of a device, the actual usefulness of it does not scale along with it. With very high yield weapons, most of the energy/blast goes up and away from the Earth, so you’re not actually destroying anything extra that you couldn’t have done with a smaller weapon better targeted.
The Russians scaled theirs down from 100 MT and still radiated a lot of their population. Russians also had plans for a doomsday ship, a large floating Navy vessel that was actually a giant neutron bomb that self detonated if radiation levels in the area reached a certain point. Only reason the Russian didn’t build it is because the design didn’t have sufficient controls to prevent unintentional detonation. If they did build it, an event like Chernobyl might have been the end of everything.
I watched a lot on the Tsar Bomba. There is an max effective detonation altitude whereas the shock wave would travel both down and outward. That detonation altitude would have to be changed on more or less powerful explosions. Hydrogen bombs are only limited by fuel supply and the ability to carry the fuel/bomb assembly. Meaning, at some point, the fuel supply maxes out the carrier’s payload capacity. The MOAB, if I’m remembering it right is rolled out of a C130.
I never head of Rod from God until now. Very interesting.
It is a lot more complicated than that, and depends on which destruction mechanism you want to use.
A low altitude airburst is going to maximize blast via the reflective wave amplifying the speed/power of the incipient blast wave (the “mach stem”). A high altitude airburst is going to maximize EMP and the light/heat radiation effect and the fireball won’t even touch the ground. A ground burst is going to maximize fallout and could also maximize damage to underground facilities.
The long and short of it is, for mach stem blast wave maximization, there isn’t a need for some dramatic increase in detonation altitude that would be impossible to achieve by existing delivery mechanisms.
The more we learn about asteroids, the less relevant I feel this is.
Hell, our biggest boom was largely a misunderstanding of Lithium 7 neutron multiplicity (making alpha particles when bombarded with high energy neutrons).
If we wanted LANL/LLNL to turn the physics package up to eleven, making a huge yield is something that stacking better tamping material (U238) and just stacking enough fissile material that the intense neutron bombardment would really spike the yield… but again, this isn’t a useful weapon for attacking a land-based adversary, which is why money got dumped into MIRVed dial-a-yield setups.